Tags in M4B files

I would like to edit the tags of my m4b files (iPod audiobook files). I can open them all in Mp3tag 2.30, and I can edit all of the tags, but after I save them, they haven't changed. They're still all blank.

Does anyone know what the trick is to saving the new tag data?




did you press the save icon on the toolbar to save the tags. If yes, can you provide me one of these files for checking this issue (I don't have m4b-files).

Best regards,
~ Florian